It is known that seeds are irradiated on all sides with low energy electrons. Electron energy and radiation dose are chosen such that the surface and near-surface layer are acted upon without any substantial impairment of the embryo (DD-PS 242 337). A device is here known which constantly redistributes the seeds with the aid of moving means within a recipient, with the seeds being acted upon by a deflected and fanned electron beam. Transporting devices which serve to supply and discharge the seeds and include the associated feeders are connected to the recipient (U.S. Pat. No. 4,633,611).
Since especially with seeds a relatively great amount of water is bound to and in the surface of seeds, the water evaporation rate is very high at the vacuum required in the irradiation chamber. This fact can only be counteracted by taking great evacuation efforts. Moreover, the process as well as the device have the disadvantage that an industrial application which calls for a great throughput is not possible because of the great dust portion of the seeds. The long-term operation of the electron gun is affected by this great dust development in the irradiation chamber.
Irradiation devices in the case of which the bulk material is guided in a free atmosphere are also known (U.S. Pat. No. 860,513 and 2,333,842). These devices are not suited for effecting any action on the surface or the near-surface layer of the bulk material exactly in the prescribed depth; in particular, phytotoxic effects on the seeds may occur because of the resultant energy dispersion.
FR-PS 961 079 discloses an irradiation device which has electron beam generators arranged opposite to each other on an irradiation chamber and in the case of which the material to be irradiated is introduced from above into the irradiation chamber and discharged therefrom downwards. Such a device, however, does not create the preconditions for an adequately individual irradiation of grainy bulk material, such as seeds, for dressing said material.
It was discovered during the conduction of the process with the known technological electron beam devices and the known bulk material delivery devices that relatively constant surface doses can only be achieved at a small bulk material throughput. By contrast, all attempts have failed to achieve a uniform surface dose as is required by the process, as well as a high utilization degree of the electron beam and a high mass throughput with the device at the same time. In other words, evacuation problems which can no longer be solved technically arise from other delivery principles that have accomplished this uniformity. However, the solution of both problems is an absolutely necessary precondition for an industrial utilization of the process.